Fatty alcohol derivatives, particularly alkoxylates, sulfates, and ether sulfates, are versatile surfactants. They are used across a broad array of industries and end uses, including personal care, laundry and cleaning, emulsion polymerization, agricultural uses, oilfield applications, industrial compositions, and specialty foamers.
Fatty alcohols are usually made by reducing the corresponding fatty acids or esters, typically by catalytic hydrogenation. Often, the catalyst includes zinc or copper and chromium. U.S. Pat. No. 5,672,781, for instance, uses a CuCrO4 catalyst to hydrogenate methyl esters from palm kernel oil, which has substantial unsaturation, to produce a mixture of fatty alcohols comprising about 52 wt. % of oleyl alcohol, a monounsaturated fatty alcohol. For additional examples, see U.S. Pat. Nos. 2,865,968; 3,193,586; 4,804,790; 6,683,224; and 7,169,959.
The fatty acids or esters used to make fatty alcohols and their derivatives are usually made by hydrolysis or transesterification of triglycerides, which are typically animal or vegetable fats. Consequently, the fatty portion of the acid or ester will typically have 6-22 carbons with a mixture of saturated and internally unsaturated chains. Depending on source, the fatty acid or ester often has a preponderance of C16 to C22 component. For instance, methanolysis of soybean oil provides the saturated methyl esters of palmitic (C16) and stearic (C18) acids and the unsaturated methyl esters of oleic (C18 mono-unsaturated), linoleic (C18 di-unsaturated), and α-linolenic (C18 tri-unsaturated) acids.
Among fatty alcohols with internal unsaturation, oleyl alcohol has been used as a starting material to make ether sulfonates that have surfactant properties (see, e.g., U.S. Pat. Nos. 7,427,588 and 7,629,299).
Monounsaturated feedstocks having reduced chain length have potential value for making surfactants, but the feeds have not been readily available. Recent improvements in metathesis chemistry (see, e.g., J. C. Mol, Green Chem. 4 (2002) 5 and U.S. Pat. Appl. Publ. Nos. 2010/0145086, 2011/0113679, and 2012/0071676) will soon make such reduced chain unsaturated feedstocks available, but alternatives are needed.
Undecylenic acid (10-undecenoic acid) is produced industrially along with heptaldehyde by pyrolyzing the ricinoleic acid in castor oil (see U.S. Pat. No. 1,889,348; J. Chem. Ed. 29 (1952) 446; J. Sci. Ind. Res. 13B (1954) 277; and J. Am. Oil Chem. Soc. 66 (1989) 938). It is used primarily to manufacture pharmaceuticals, fragrances, and cosmetics.
Undecylenic acid is easily reduced to undecylenic alcohol with hydride reducing agents (e.g., lithium aluminum hydride) or selective hydrogenation catalysts (see, e.g., J. Am. Chem. Soc. 59 (1937) 1. It is known to ethoxylate undecylenic alcohol for possible use in laundry detergents (JP 10140195). Undecylenic alcohol ethoxylates have also been studied as principal components of self-assembled monolayers, which can mimic membrane structure and function (see, e.g., U.S. Pat. No. 6,809,196 and J. Am. Chem. Soc. 113 (1991) 12).
Undecylenic alcohol has been converted to sodium 10-undecenyl sulfate, and this compound has been used as a monomer for making polymerizable surfactants (see, e.g., Electrophoresis 25 (2004) 622; New J. Chem. 16 (1992) 883; and Langmuir 9 (1993) 2949).
Sulfation of alcohols produces alcohol sulfates, which have an C—O—SO3X group, where X is typically an alkali metal or ammonium ion from a subsequent neutralization step. Sulfonation of unsaturated hydrocarbons gives sulfonates, which have a C—SO3X group. When an unsaturated alcohol is the starting material, the unsaturated sulfate can be produced under some conditions (see, e.g., WO91/13057). With other reagents, alcohol sulfation and carbon-carbon double bond sulfonation may compete, with most of the reaction product resulting from sulfation, although the nature of the sulfonated by-products is generally not well understood (see, e.g., U.S. Pat. No. 5,446,188). Because of the competing side reactions, unsaturated alcohols are usually avoided when the goal is to make an alcohol sulfate or ether sulfate.
In sum, despite the known value of longer-chain fatty alcohols and shorter-chain saturated fatty alcohols for making ethoxylates, sulfates, and ether sulfates for use as surfactants, it is less clear what value the surfactants would have if they were made using shorter-chain unsaturated (e.g., C10-C12) fatty alcohols. The availability of undecylenic acid and undecylenic alcohol as feedstocks invites further investigation.